Nice find wxlt!
I'm standing in line at the Magic Kingdom waiting to meet Elsa and Anna from Frozen. I figure I have a few minutes to read and post... ☺
In the case of GaAs power amps in mobile devices, it's a buy one get one scenario. For every function usually requiring a Si chip which can be pulled onto the GaAs PA, we save the cost of another Si chip plus the interconnections as fairchij mentioned.
Costs aside, its also fun to speculate on what addional functions might be added to mobile devices when the extra real estate is freed up with full POET integration!